The objective of the AWII pear program was to determine whether eliminating certain insecticides known to be disruptive of many natural enemies in pear orchards could improve the biological control of several key pear pests, including pear psylla, spider mites and grape mealybug.
Six pear orchards participated in the AWII program. Each orchard was divided into four treatment-blocks:
- AgriMek and OP insecticides used (OP +AG)
- AgriMek used, no OP insecticides used (noOP +AG)
- No AgriMek, OP insecticides used (OP noAG)
- No AgriMek, no OP insecticides used (noOP noAG)
Each orchard was monitored with CM pheromone traps and low-load leafroller pheromone traps for both the obliquebanded and pandemis leafroller. DA (a pear ester) and AA (acetic acid) lures, both containing non-pheromone attractants, were also used in the pear orchards for monitoring CM and leafrollers, respectively. Traps were checked weekly and the number of moths recorded. Every two weeks, each of the four treatments in each pear orchard was monitored separately for pear pests and natural enemies by taking a 20 beat-tray sample. Leaf samples were collected at two-week intervals from each treatment from fruiting spurs (mid May through August) and top shoots (mid-June through August). These leaf samples were brushed and counted at the WSU-TFREC or the USDA-YARL. Field assessments of CM damage were conducted in all treatments in each pear orchard, and the consultants conducted harvest time examinations of fruit in each orchard (1500 fruits/treatment, four treatments/orchard).
Pear psylla: Psylla is the major pest for most pear growers, and was controlled well at all AWII sites. Psylla populations varied considerably and were consistently higher in the North Central Washington (NCW) sites (P4-P6) than in the Yakima sites (P1-P3) (Table 2 and Figure 2). Post-bloom counts of psylla adults exceeded 0.5/tray in only two of 80 samples in Yakima but were over that level in 34 of 80 NCW samples. Similarly, summer counts of pear psylla nymphs never exceeded an average of 0.1/top shoot leaf in any of the 12 Yakima treatment-blocks while nine of 12 NCW blocks had average nymph counts above 0.1/leaf (Figure 3). There was a late season increase in psylla nymph numbers in most NCW blocks, but not in most Yakima blocks. Psylla adult numbers tended to be higher in the non-AgriMek (noAG) treatment blocks in NCW, although there was no significant difference in nymph counts.
Table 2. Counts of key pear pests in Areawide II pear blocks, 2001
|N/tray||N/shoot leaf||N/lower leaf||N/tray|
|Grower||Treatment||(May-Aug avg)||(Jun-Aug avg)||(Aug avg)||(Aug avg)|
- Spider mites: Twospotted spider mite was the most common mite species found, but occurred only at low levels. Counts exceeded 0.5 mites/leaf in only four of the 360 samples examined (Table 2). European red mites were found in only three leaf samples, all at one orchard (P2).
- Pear rust mite: Rust mites were found in leaf samples from only one orchard (P3). All four treatment-blocks at this orchard had rust mites on at least three separate dates. No fruit russet from rust mites was found in this orchard or any others.
- Grape mealybug: This pest was found in all three NCW pear orchards, but in none of the Yakima orchards. Mealybug was counted on tray samples and August shoot samples in all 12 treatment-blocks in NCW (Table 2 and Figure 4).
- Codling moth: There was a wide range in codling moth (CM) populations among the six sites. Sites P1 and P2 in Yakima had the total catch in pheromone traps for the season average less than 2 moths per trap, while sites P4 and P5 averaged 14 and 24 CM/trap/season, respectively. Second generation CM catches were higher in all NCW orchards, but remained low in the Yakima sites. DA lure-baited traps caught few moths in these pear orchards, never exceeding an average of 2.5 moths/trap season. The CM catch in DA traps showed no correlation with the catch in pheromone traps in these orchards.
- Leafrollers: Pandemis leafroller was caught in five of six orchards and was the dominant species in four, including all Yakima sites. Obliquebanded leafroller was caught in only two orchards (P4 and P6) in NCW, and was the dominant species only in P6. Acetic acid (AA) lures were used to monitor leafrollers in all blocks and caught far fewer moths per trap than traps baited with the low load pheromone lures. The leafroller catch in AA traps had a fair correlation with PLR catches but was not correlated with OBLR catches.
- Natural enemies: Nine types of predators and parasites were counted in this project: deraeocoris, campylomma, anthocorids, lacewings, lady beetles, stethorus beetles, spiders, Trechnites sp. (a key psylla parasitoid), and parasitic hymenoptera in general. The most common, and most significant in terms of potential biological control, were deraeocoris, campylomma, lacewings, Trechnites sp. and spiders (Table 3 and Figure 5). Natural enemy counts were much higher on average in the NCW orchards. This may have been a result of more suitable habitats (nearby wooded and riparian areas that served as natural enemy reservoirs), more food (psylla) to attract and retain them, and, in several blocks, less use of disruptive insecticides. In the Yakima treatment-blocks the sum of the five major natural enemy types never exceeded 0.05/tray in any summer sample, while in NCW all blocks exceeded that level. The highest natural enemy counts occurred in P6, with the no AgriMek blocks (that relied upon oil and Ecozin for psylla control) having far higher counts than the AgriMek blocks.
Table 3. Counts of key natural enemies in Areawide II pear blocks, 2001
5 NE classes
Jun to Aug averages
All treatment-blocks had 1500 pears examined during harvest for pest damage (Table 4). Russet caused by pear psylla was detected in 20 of 24 blocks but at generally acceptable levels. Fruit was considered marked if the cumulative area of psylla-caused russet exceeded the area of a nickel. The amount of fruit marking was best correlated with the psylla nymph counts on top shoot leaves in July, especially in NCW, but poorly correlated with August counts. Grape mealybug counts reflect fruits infested with nymphs, and these infestations were only found in NCW. Fruit infestation was a particular concern in orchard P4. Fruit infestation levels were weakly correlated with August tray counts of mealybugs, but not correlated with August shoot counts. Codling moth damage was below 0.4% on average in all orchards. The two orchards with the highest CM catches (P4 and P5) had no damage detected at harvest. The highest average damage occurred in P3 and P6, both of which had one treatment-block with higher damage that may require additional treatment in 2002. Leafroller damage was found at a low level in all orchards, averaging less than 0.2% at all sites, and exceeded 0.5% in only one treatment-block (in P5). Other pest damage was found at low and variable amounts and was caused by cutworms and lygus (Yakima sites in particular), stink bug/boxelder bug (especially NCW), and San Jose scale (blocks in P3 and P6).
Table 4. Fruit evaluations at harvest (1500 fruits per treatment-block)
* denotes 0.00%; GMB = infested fruit (not russett)
Foliar applications of pesticides are summarized in Table 5. AWII pear growers used a diverse range of spray programs. The number of individual pesticide applications in a treatment-block ranged from 7 to 27. AgriMek (AG) was used in all 12 blocks in which it was part of the protocol. Organophosphate (OP) use was limited by the lack of need. Only 8 of 12 blocks calling for OPs in their protocol actually applied an OP. Other common insecticides used included:
- Esteem - applied in 17 of 24 treatment-blocks, and 10 of 12 noAG blocks.
- Pyramite - used in 11 blocks (seven with AgriMek, four without).
- Intrepid - used in nine blocks, and for CM/leafroller control in six noOP blocks.
- Surround - used prebloom in most NCW blocks, but in no Yakima blocks.
- Oil - applied in all blocks. Three to nine applications were made, with up to five post-bloom sprays.
- Actara/Provado - these neonicotinoids were applied to 14 blocks, and 10 of the 12 Yakima blocks.
- Ecozin - this azadirachtin product was used only in NCW, applied from one to eight times. It was applied in eight blocks, and in all six NCW noAG blocks.
- Codling moth mating disruption - used in only three orchards (P1, P2, and P6) across all treatments.
The cost per acre for individual treatment-blocks ranged from $153 to $635. The average cost per treatment type was similar among the four types, ranging from $375 for the AG+OP blocks to $420 for the noAGnoOP blocks.
Table 5. Foliar pesticides in AWII pear blocks, 2001
1 material x 1 date x 100% coverage = 1 application
Ag=AgriMek; OP=organophosphate; Es=Esteem; Py=Pyramite; Su=Surround; Oil=spray oil; PA=Provado & Actara; Ec=Ecozin;
|Number of sprays|
The Areawide II pear blocks will be followed for at least two more years. The goals of the pear program remain the same: develop a pest management program with reduced inputs, reduced cost, more natural enemies and greater stability. Monitoring protocols will be very similar in 2002, but the use of AA lures for leafrollers will be discontinued. The treatment protocols will be revised into just two regimes to better focus on insecticide impacts on pests and natural enemies.